The search for and recovery of oil is becoming increasingly difficult as world-wide petroleum reserves decline. In many instances, reserves trapped within certain low permeability formations, such as certain sand, carbonate, and/or shale formations, exhibit little or no production, and are thus economically undesirable to develop at current oil and gas prices. In certain unconventional formations, such as low permeability formations, the most important element that determines whether developing reservoir will be economically viable is finding sweet spots in the reservoir. It is well established that tight gas wells can become commercially viable when a sweet spot is encountered. A sweet spot is generally defined herein as the area within a reservoir that represents the best production or potential for production. Unfortunately, current technologies are unable to locate or predict when and where sweet spots exist within a given formation.
Tight sands and shale are gas bearing but very low permeability formations, and thus present difficulties in recovering hydrocarbons therein. Due to the high demand on clean fuels, however, they are becoming important development targets. To make these low permeability formations suitable for producing commercial quantities of gas, stimulation using massive hydraulic fracturing is typically required. Generally, hydraulic fracturing stimulation treatments aim to maximize the sand face surface exposed to the producing well. The stimulation process also entails activating the near well bore fractures to enhance the conductivity of the sand face. The fracturing treatment is often logistically very challenging and therefore can be commercially very cumbersome. What makes production from tight sands and shale more promising, and therefore more commercial, is when the well is placed in a prolific area of the reservoir. This area is referred to by geologists and reservoir engineers as sweet spot. In some rare and lucky occasions, a sweet spot is encountered where a well is drilled. The economics are therefore significantly improved if a well encounters a sweet spot of the reservoir. The chances of encountering the sweet spot, however, are low.
Exploration efforts and research have focused on searching for reservoir sweet spots to improve project economics and maximize well success. Sweet spots, however, are often merely very thin streaks in tight formations. The current exploration technologies are, to a certain extent, helpless in detecting them.
In tight reservoirs, due to low permeability of the formation, well productivity is typically low, thus making the well non-economical from a standpoint of development. Stimulation treatments are one known method that can be used to enhance well productivity and improve the economics of developing the well. One commonly employed technique for stimulating low productivity wells is massive hydraulic fracturing, which typically involves the injection of high viscosity fluids into the well at a sufficiently high rate so that enough pressure is built up inside the wellbore to split the formation apart. Often these hydraulic fracturing treatments must be done in several stages to maximize reservoir contact and reservoir volume that is stimulated. The resulting hydraulically induced fracture that is produced extends from the wellbore deep into the formation.
Stimulation procedures can employ several techniques to insure that the induced fracture becomes conductive when injection is ceased. For example, during acid fracturing of carbonate formations, acid based fluids are injected into the formation to create an etched fracture and conductive channels, which are left open upon closure of the fracture. In use with sand or shale formations, a proppant can be included with the fracturing fluid such that the induced fracture remains propped open as it closes. These methods, however, have limited uses. For example, because shale and sandstone formations do not react with acids, acid stimulation fluids are typically not employed, and only hydraulic fracturing with proppants is employed, and multiple stages of fracturing are frequently necessary. Multistage fracturing has raised many concerns due both to the high cost and because of the very large amounts of water that are required.
Thus, additional needs exist for the ability to enhance production within a tight gas formation to enhance production thereof. Specifically, methods and compositions having low environmental impact are needed for the creation of synthetic sweet spots.